A major aim of modern neurobiology is to define the cellular and molecular mechanisms contributing to memory formation. The large library of behaviorally isolated Drosophila learning mutants has been useful in identification of specific genes (including dunce, rutabaga, latheo) and signal transduction cascades (cAMP-PKA- CREB) that contribute to different aspects of olfactory associative learning. It is clear from studies at the NMJ and in embryonic cultures, that many of these genes and signaling pathways can regulate neural function. However, since neurons in the brain of the tiny adult fly have been inaccessible to electrophysiological recording, it has not been possible to use this outstanding genetic resource to explore how these genes regulate function in central circuits involved in memory formation. Our preliminary studies demonstrate that we can now routinely record from identified neurons in whole brains isolated from adult flies. Robust spontaneous activity indicates circuits are functionally as well as structurally intact. We have also developed conditions that support the formation of functional synaptic connections between identified neurons in cultures prepared from late stage pupal brains. The current proposal utilizes these two preparations and takes advantage of the molecular genetic strategies feasible in Drosophila, to examine the role of cAMP signaling in regulation of activity in neuronal circuits that process information during olfactory associative learning. Experiments are focused on antennal lobe projection neurons that receive information directly from the olfactory receptor neurons in the periphery, and Kenyon cells, their targets in mushroom bodies, an association area involved in formation of olfactory memory. The results of these studies should [provide unique insights into the cellular and molecular mechanisms involved in regulation of activity in central circuits that process information during olfactory associative learning.